1. Field of the Invention
The invention generally relates to distributed optical network management systems and methods. The invention more particularly relates to methods and systems that perform distributed optical network management of faults and alarms.
2. Description of Related Art
Optical communication systems are a substantial and fast growing constituent of communication networks. The expression xe2x80x9coptical communication system,xe2x80x9d as used herein, relates to any system which uses optical signals to convey information across an optical waveguiding medium, for example, an optical fiber. Such optical systems include but are not limited to telecommunication systems, cable television systems, and local area networks (LANs). (Optical systems are described in Gowar, Ed. Optical Communication Systems, (Prentice Hall, New York) c. 1993, the disclosure of which is incorporated herein by reference.)
Currently, the majority of optical communication systems are configured to carry an optical channel of a single wavelength over one or more optical waveguides. To convey information from multiple sources, time-division multiplexing (TDM) is frequently employed. In TDM, a particular time slot is assigned to each signal source with the complete signal constructed from portions of the signal collected from each time slot. While this is a useful technique for carrying plural information sources on a single channel, its capacity is limited by fiber dispersion and the need to generate high peak power pulses.
While the need for communication services increases, the current capacity of existing waveguiding media is limited. Although capacity may be expanded (e.g., by laying more fiber optic cables), the cost of such expansion is prohibitive. Consequently, there exists a need for a cost-effective way to increase the capacity of existing optical waveguides.
Wavelength division multiplexing (WDM) is being explored as an approach for increasing the capacity of existing fiber optic networks. WDM systems typically include a plurality of transmitters, each respectively transmitting signals on a designated channel or wavelength. The transmitters are typically housed in a first terminal located at one end of a fiber. The first terminal combines the channels and transmits them on the fiber to a second terminal coupled to an opposite end of the fiber. The channels are then separated and supplied to respective receivers within the second terminal.
The WDM system described in the previous paragraph can be perceived as a point-to-point connection with multiple signals carried from one terminal to the other. However, it is frequently advantageous to add and drop channels at various locations between the two terminals. Accordingly, other network elements, such as add/drop modules are often provided along the fiber in order to inject and/or remove channels from the fiber. Moreover, if the fiber extends over long distances, it is necessary to segment the fiber into sections with each fiber section being coupled to another by an additional network element that amplifies the signal (e.g., an erbium doped fiber amplifier).
In addition to the information bearing channels described above, Condict ""115 utilizes a service channel at a wavelength different than the information bearing channels and carrying diagnostic and span topology information can also be transmitted through each span. Information associated with a span may be coupled via Ethernet connections to an internet protocol (IP) router. This IP router passes the information via the Internet to additional IP routers. A local area network (LAN) then transmits the information between the IP routers and to the network monitoring equipment. Finally, information associated with a span is similarly passed to network monitoring equipment through Ethernet links and an IP router.
The Condict ""115 patent ensures proper operation of the WDM system by monitoring each network element. In the event of a failure, such as a fiber break, the communication system maintains its ability to monitor each network element by using, for example, a service channel separate from the main optical communication channel. Moreover, the communication system automatically responds to a fault by having each network element identify itself and report information about its operating status.
The Condict ""115 patent further includes an optical communication path and a plurality of network elements disposed along the optical communication path. A first network element coupled to the optical communication path includes a first processor and a first optical component. The status of the first optical component is monitored by the first processor. The first processor generates a first electrical signal in accordance with the status of the first optical component. The first network element also includes a service channel transmitter coupled to the first processor and emits a second optical signal to the optical communication path at a second wavelength different than the first plurality of wavelengths in response to the first electrical signal. The second optical signal being modulated in accordance with the second electrical signal. A second network element is coupled to the optical communication path and includes a second processor, a second optical component coupled to the second processor and a service channel receiver coupled to the first processor and to the optical communication path. The receiver senses the second optical signal. The service channel receiver outputs a second electrical signal to the second processor in response to the second optical signal. The second processor controls the second optical component in response to the second electrical signal.
The Condict ""115 patent span management systems and methods manage a span of an optical network in which each network element exchanges identification and status information for performing various monitoring and control functions in the optical network.
Condict ""115 provides powerful and effective solutions for managing an optical communications network. The present invention expands upon these capabilities by more effectively managing multiple spans and solving the diverse challenges presented by the management and control of complex communication networks having a variety of topologies and span designs.
The present invention includes systems and methods that manage a communications network having a single span or multiple spans. The features of the invention may be added to a conventional communications network such as an electrical, optical, or electro-optical communications network in which a plurality of network elements convey information over one or more links or spans of the network. Furthermore, the inventive systems and methods and may be integrated into various proprietary, standard, and future-developed communications systems or methods including multiplexed [e.g. TDM (time division multiplexed), WDM (wave division multiplexed), or nonmultiplexed communications systems.
One of the implementations of the inventions includes incorporating or otherwise utilizing central processing elements distributed across network elements of a communications system. Either some or all of the network elements having such central processing elements may be programmed with a distributed intelligence and utilize a distributed database to intelligently manage the network
The management features of the invention include distributed management of faults, alarms, and various network topology and control information.
A fault is any condition, error, failure, or problem that may cause or contribute to an immediate or future negative impact on a communications network. The types and varieties of faults are too numerous to exhaustively list here and are dependent upon the exact equipment and methods used by the communications network but some examples are a failure or degradation of an amplifier, multiplexer, demultiplexer, fiber, switch, software, service, nodal control processor or components thereof such as a fiber grating outside its operating temperature range or a pumping laser not operating within nominal parameters provisioning errors, missing equipment, transmitter failures, receiver failures, power failures, signal level degradation, software errors, and communications errors.
Upon detecting any such fault, that fault is reported to the central processor of the network element responsible for monitoring faults occurring on the portion of the network in which the fault occurred.
The network element processor, according to the invention, receives a fault report (or fault object) indicating that a fault has occurred and determines whether the fault is sympathetic to another fault in the network. In other words, the network element processor determines if the fault was caused by another fault in the network. Sympathetic faults are suppressed by not reporting them to other network element processors.
For non-sympathetic faults, the network element processor asserts an alarm and also determines whether the fault affects other circuits. For example, when an amplifier amplifying several channels of a WDM (wave division multiplexed) signal fails several channels will be affected. These affected channels are examples of circuits that may be affected by a fault. The invention informs other network element processors in the network for each such affected circuit by, for example, broadcasting an alarm object data item throughout the network to the affected network element processors.
The term xe2x80x9ccircuitxe2x80x9d as used herein is a broad term and may include a variety of different elements. For example, a typical high capacity communication network may include multiple levels of multiplexing one of which may be time division multiplexing (TDM) which takes multiple customer circuits and aggregates them into a single wavelength of a wavelength division multiplexed system. These wavelengths may then be aggregated into routerbands, and then these routerbands may be aggregated into a composite signal which is fed to the line amplifiers. A circuit, as used and defined herein may include any of these levels of multiplexing and may be generally described as the simplex path of data from the ingress point into the network, through the network and finally to an egress point in the network. An example of a simple circuit is the customer signal arrives as a transmitter, the signal is modulated to a different wavelength and multiplexed into the fiber and then finally received and demodulated back to the customer.
Moreover, the relationships between the alarms may be between common equipment (e.g., amplifiers) and circuits; common facilities (e.g., fiber) and circuits; circuit specific equipment (e.g., transceiver equipment failures) and circuits as well as conditions reported at downstream equipment.
In addition to the processing of the alarms by the network element processors, the alarms may also be received by a network manager or interface which displays the alarm information to a user such as a technician attempting to diagnose and correct the fault. As the complexity of communications networks increase so does the number and complexity of potential faults and alarms. Indeed, without the inventive systems and methods the technician could be presented with a bewildering array of alarms and would have great difficulty diagnosing and correcting the problem(s) that triggered the alarms.
The invention reduces the number of alarms (as well as the reporting of underlying faults) by performing distributed alarm correlation and fault reporting suppression. The number of alarm and fault data objects further reduced by appropriately clearing both the alarm and original fault object that triggered the alarm from the database in which they are stored.
The database is preferably a distributed database that is distributed across each of the network element processors. The database not only stores the fault and alarm objects but also network topology information such as the address, identity, connectivity, and functionality of each network elements and components thereof. The database, also termed xe2x80x9cspan databasexe2x80x9d herein is utilized, inter alia, to determine the root cause of a fault, identify sympathetic faults, determine what affect a fault has on other circuits, etc.
By utilizing the distributed span database, the distributed network element processors can readily identify the root cause of faults, suppress the reporting of sympathetic faults to other NEPs, and generate appropriate alarms for that are advertised (broadcasted) to other NEPs. The distributed span database is particularly useful when correlating faults to other alarms and faults so as to detect causality. These capabilities permit more expeditious identification of problems and implementation of remedies to address the problem.
One of the inventions includes a distributed method of controlling a communications network having a plurality of spans of interconnected network elements wherein at least two of the network elements on each span include a network element processor, including: distributing network topology information to respective span databases at each of the network element processors; storing original fault objects in the respective span databases at the network element processor responsible for monitoring the occurrence of each of the original faults occurring in a respective span of the communications network; advertising fault objects to other network element processors in a local span when the original fault affects network elements other than a network element in which the fault occurred; advertising alarm objects to other network element processors that are respectively associated with a circuit affected by the original faults; storing the advertised fault and alarm objects in the respective span databases; and performing distributed processing of the advertised fault and alarm objects with the other network element processors and the respective span databases.
This distributed processing may also include correlating the alarm and fault objects at each of the network element processors; clearing fault and alarm objects from the respective span databases; advertising an alarm object to other network element processors respectively associated with a circuit affected by the fault or alarm object being cleared; correlating fault objects being cleared with other fault and span objects; suppressing reporting of the original fault object to other network element processors when the original fault object is sympathetic to another fault; and/or correlating the advertised alarm objects with other alarm objects and fault objects to determine a root cause of the advertised alarm objects.
Another of the inventions includes a method of controlling a network element to perform distributed management of a communications network having at least one span, including: receiving a fault; aggregating other faults, one or more alarms associated with the fault and one or more alarms that may be occurring on the communications network due to other faults other than the received fault; and correlating the other faults and the one or more alarms with the received fault to determine if the received fault is sympathetic to at least one of the alarms or the other faults.
Furthermore, the aggregating step may introducing a delay related to a number of network elements in the communications network.
If the communications network includes multiple spans, then the method may include multispan aggregating one or more multispan alarms associated with the received fault and one or more multispan alarms that may be occurring on the communications network due to the other faults; and multispan correlating the one or more multispan alarms with the received fault to determine if the received fault is sympathetic to at least one of the other faults or at least one of the multispan alarms.
Another inventive method controls a network element processor of a communications network having at least one span, including: associating a received fault, received by the network element processor, to a circuit topology of the communications network; determining whether the received fault is sympathetic to at least one other fault or alarm in a same circuit as the received fault based on said associating step; and suppressing reporting of the received fault to a network monitoring interface of the communications network when the received fault is sympathetic to the at least one other fault or alarm in the same circuit.
The invention may also determine if the received fault affects at least one other circuit different than the circuit associated with the received fault; and advertise the alarm object to all network element processors associated with each of the circuits affected by the received fault.
The invention also includes a method of building a database of circuit topology information; and storing the database in each of the network element processors to create a distributed span database that may be used, inter alia, to determine whether the received fault is a sympathetic fault.
Yet another invention processes span alarm objects in a communications network having a plurality of network elements including a first network element and a second network element by adding a current span alarm object to a database of the first network element; determining if the current span alarm object corresponds to an existing span alarm object previously received by the first network element; incrementing an instance count associated with the existing span alarm object when said determining step determines correspondence between the current span alarm object and the existing span alarm object; and storing the current span alarm object in the database when the determining step determines no correspondence between the current span alarm object and the existing span alarm object.
The instance count may be decremented when the current span alarm object is being cleared and when the instance count reaches zero the invention correlates at least one child alarm object that is a child of the current span alarm object (e.g., sympathetic to the current span alarm object being cleared) with other fault or alarm objects.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.